Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds useful behavior beyond that: results include a resizer link per size, and an empty platform enumerates all platforms. It says nothing about result volume or whether the catalog is static, which would matter for a full listing.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences with the resource scope front-loaded and the empty-platform rule tucked in before the return-value note. No filler, though the trailing clause about the Six-IR resizer could be tightened.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-optional-parameter read-only lookup with no output schema, the description covers what is returned (pixel sizes plus a resizer link) and how to broaden the query. Only the relationship to the sibling make_resize_link is unaddressed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both parameters are already documented with examples. The description contributes the empty-string semantics for platform, which the schema does not state, but adds nothing for kind beyond what the schema already says. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (recommended image size lookup in pixels) and enumerates the asset types covered (posts, stories, covers, thumbnails, banners, profile photos), which makes the tool's scope immediately legible. It does not name or distinguish itself from the sibling make_resize_link, so it falls short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The only usage guidance is "Leave platform empty to list every platform," which clarifies one calling pattern but gives no when-to-use/when-not-to-use framing. There is no pointer telling the agent to use make_resize_link when it actually wants to generate a resize URL rather than read the size table.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.